The goal of this proposal is to examine the mechanism(s) through which covalent binding of neurotoxicants (acrylamide, carbon disulfide (CS2), 2,5-hexanedione (2,5-HD)), to cytoskeletal proteins produces a dying back type of neuropathy. The present study is motivated by the pathological findings that many compounds which covalently bind with specific amino acid residues produce a dying back type of neuropathy. Common neuropathological features of many of these types of neuropathies include axonal swellings which may contain a high number of neurofilaments. Understanding the underlying mechanism which produces this type of neuropathy is primarily important for the elucidation of chemically induced injury to nerve cells. The hypothesis of this proposal is that acrylamide, carbon disulfide, and aliphatic hexacarbons directly interfere with neurofilament function. Several possible alterations of neurofilament biochemistry will be investigated. The mechanisms through which these alterations occur involve a direct binding of the toxicant to neurofilament proteins, an inhibition of protein phosphorylation, an inhibition of proteolytic proteins. The specific aims of this proposal are (1) to examine the in vitro and in vivo covalent binding of [14C]labeled neurotoxicant to cytoskeletal and identification of the amino acid residue which is bound, (2) to study in vitro protein phosphorylation after in vitro incubation with neurotoxicants or in vivo exposure to neurotoxicants, (3) to study in vitro and in vivo proteolytic breakdown of neurofilaments, (4) to examine the reconstitution of neurofilaments after in vitro exposure of neurofilaments to chemicals, (5) to study the interaction of neurofilaments with microtubules and microtubule associated proteins in vitro after in vivo exposure of cytoskeletal proteins, (6) Quantitate change in specific epitopes of neurofilament proteins (i.e. phosphorylated versus de-phosphorylated epitopes) after exposure to these chemicals, and (7) to determine if a protein kinase which is associated with neurofilaments is specifically altered by vivo treatment or in vitro incubation with these neurotoxicants.